Copper (Cu) is one of the most important metals in modern technologies. In nanotechnology (e.g., nano-optoelectronic industry), fabrication of one-dimensional (1D) nanomaterials of copper (wires/cables/rods) have received considerable attention in recent years. A number of fabrication methods have been proposed including electrochemical reactions, vapor depositions, soft and hard template processes, reverse micellar systems, etc. So far, effective methods for large-scale production of high quality nanostructured copper or metal nanowires with precise morphological control have not been realized. Fabrication problems may include short length, nonlinear morphology, polydispersivity, poor crystallinity, low yield, and/or process complexity.
Conventionally, copper nanowires have been prepared by the synthesis of sodium hydroxide and cupric nitrate (an aqueous solution) in a glass reactor. The general redox reaction is:2Cu+2+N2H4+4H−→2Cu+N2+4H2O
In “Large-Scale Synthesis of High-Quality Ultralong Copper Nanowires,” Langmuir 2005, Volume 21, pp. 3746-3748, Yu Chang, Mei Ling Lye, and Hua Chun Zeng, varying amounts of ethylenediamine (EDA) and hydrazine are added sequentially to the aqueous solution, followed by a thorough mixing of all of the reagents. The reactor was then placed in a water bath with a temperature control over 25-100° C. for 15 minutes to 15 hours. The copper products were washed and harvested with centrifugation-redispersion cycles and stored in a water/hydrazine solution to prevent oxidation. The prepared nanowires are straight with constant diameters in the range of 60-160 nm. The length of the nanowires is greater than 40 μm, which corresponds to an aspect ratio of greater than 350. Further, Chang et al. discusses forming single crystalline nanowires with high lattice perfection. One of the disadvantages of the copper nanowire described in the “Large-Scale Synthesis of High-Quality Ultralong Copper Nanowires” is the surface oxidation of copper. Further, the nanowires discussed in “Large-Scale Synthesis of High-Quality Ultralong Copper Nanowires” do not possess additional functionalities to meet their future new applications.
However, there is still a need in this technical field for improved methods for the preparation of copper (Cu) nanowires, nanotubes, and nanorods.